ConfigImporter::notify() uses the ConfigImporter::ID to construct the event id string. I found that this ID was introduced in #1890784: Refactor configuration import and sync functions, but is now only used in ConfigImporter. This patch removes the usage of ID for events, and instead used ConfigEvents::IMPORT and ConfigEvents::VALIDATE.

The method ConfigImporter::getId() is renamed to ConfigImporter::getLockId(). I removed getId in the previous patch, but the ID it was used to test the lock. Renamed the method to explains the meaning of the ID better.